The invention concerns a process for manufacturing by means of extrusion composite sections or similar products comprising at least two component sections whereby one of the sections is introduced into the stream of metal which is the matrix, in particular a light metal matrix, as it is being extruded and concerns too a device with an extrusion tool having at least one die hole for carrying out this process.
A process is known whereby several steel wires are fed into the extrusion tool, parallel to the long axis of the tool, and leave it in the form of a reinforced section with the wires surrounded by the extruded matrix. The application of this process remains restricted to the production of internally reinforced sections.
In the case of another standard process for producing composite sections, a roll-clad metal strip is introduced into the chamber of an extrusion press die, and by applying a compressive force to the side which is not clad, is metallically bonded to the extruded section which is made of an appropriate material.
In view of this state of technological development, the inventor set himself the task of working out a process and device of the kind mentioned at the beginning, whereby non-clad metal strips or similar components could be intimately bonded to the matrix. Thereby, rubbing between the metal strip and the extrusion tool should be avoided and economical production of composite sections for many applications should be realized at a favorable cost.
These problems are solved by means of a process by which two separate sections or strips lying face to face are fed into the die and the strips bond intimately with the matrix which constitutes the other component and do so on the sides of the strips facing away from each other and at the same time the sides of the strips in contact with each other do not bond with each other, nor with the matrix. Each strip is then metallically bonded to the matrix on the side of the strip facing away from the other strip.
According to another feature of the invention, the two strips or similar sections run during the extrusion process in the separating plane between two neighboring holes in the die for simultaneous production of a pair of extrusion sections, preferably in the axis of symmetry between two openings of identical outline. In this way also several pairs of strips, spaced apart from each other, can pass through the hole in the die, whereby these composite sections are produced between any two particular pairs of strips.
This process has the advantage over other composite manufacturing process of utter simplicity because the joining of the section body to the covering layer requires no additional manufacturing step; the joining takes place during extrusion. The method of the invention also achieves considerable improvement over other methods of extruding composites in which the material of the composite comes into abrasive contact with the extrusion tool, because in accordance with the invention the composite material passes through the tool with the little contact and therefore without causing abrasion and is successfully bonded to the surface of the section. The cladding layer remains protected between the two neighboring, simultaneously extruded sections and, in addition, permits these sections to be separated without effort at the exit side of the die.
By appropriate preparation of the strips of cladding material, they can, in accordance with the invention, be mechanically engaged in the matrix by virtue of their shape, without it being disadvantageous to the separating of the sections. In the case of metallic bonding of the components, a suitable pretreatment is necessary viz., heating the strips and removing the oxide layer from the side which is to be bonded to the matrix.
In this way one can, for example, metallically bond a layer of stainless steel to an aluminum section and achieve a bond strength which is of the order of magnitude of the fracture strength of the matrix.
Such a bond strength, which can also be further aided by mechanical engagement due to appropriate shaping of the strip in the form of sloping edges along its length, allows the process of the invention to be used in particular for the manufacture of composite conductor rails due to the good interface properties with respect to mechanical strength corrosion and electrical resistance. It is of no consequence whether the section produced is a full or hollow section.
It has been found favorable to manufacture sections with a cladding layer in the form of a flat strip which is supplied and used in the tool without plating or covering with another metal or material. What is preferred, for example, are two strips of electrolytic copper which are joined to the matrix in a sandwich-like manner to give a rod like section, several of which can be extruded simultaneously without difficulty.
As many conductor rails are stressed only by clamping at certain points, there is a conductor rail or similar item produced by the process of the invention consisting of a core with a strip cladding which along its length is alternately of steel and non-ferrous metal; these lengths of strip of different material can be joined together at their ends in the described process without interrupting the continuity of the process.
It is a part of the invention that the strips or similar component parts are introduced as pairs in a common stream into the side of the extrusion press tool, or also as separate strips into different sides of the tool, and deflected through the tool to the die hole, and in the case of separate strips are brought together. This procedure permits continuous composite extrusion; the cladding material is fed into the side of the extrusion tool independent of shearing, billet loading, etc.